Preparation of cyanformimide esters



United States Patent 3 Claims. ci. 260-453 This invention relates to thepreparation of cyan-formimide esters.

It is known in the art that alcohols react with cyanogen in the presenceof alkaline catalysts, and such a reaction is generally performed bypassing gaseous cyanogen into an alcohol having dissolved therein analkaline compound (such as an alkali alcoholate or an alkali cyanide)which catalytically influences the reaction. In such a reaction,mixtures of cyanfor-mimide esters and oxalic acid di-im-ide esters arealways obtained, i.e. mixtures of products formed by reaction of one molof alcohol'per mol of cyanogen (cyan-formimide esters) and of two molsof alcohol per mol of cyanogen (oxalic acid di-imide esters):

The term R refers to the hydrocarbyl portion of the alcohols belowlisted. Although the prior art teaches means by which either themono-addition product or the di-addition product can be obtained inpredominant quantities, no process has previously been known whichproduces with strong selectivity substantially only the monoadditionproduct, i.e. the cyantor-mimide ester of the alcohol employed. Suchcyanformimide esters have insecticidal and insect-repelling properties,and can be used as pesticides either alone or in admixture with hydrogencyanide and/or cyanformic acid esters. Cyanfornn'mide esters are alsouseful as intermediates in the synthesis of cyanformic acid esters, forexample according to the process described and claimed in copendingapplication Serial No. 261,884 filed on even date herewith.

According to the present invention, cyanformimide esters are obtainedwithout simultaneous formation of corresponding di-addition products(oxalic acid di-imide esters) when the reaction between cyanogen and analcohol takes place in the presence of small amounts, advantageouslybetween about 0.5 and about percent by weight of the alcohol reacted, ofa tertiary alkyl amine having from 1 to 6 carbon atoms in each of thealkyl groups. As exemplary of materials of this type, trimethyl amine,tributyl amine, trihexyl amine, and mixed amines such as diethylbutylamine can be mentioned.

The formation of the ester product according to the invention preferablytakes place at low temperatures, 'for example from about 0 C. to aboutC. Nevertheless, and particularly for the reaction of higher boilingalcohols, higher temperatures of, for example, up to or over about 50 C.are suitably employed. The reaction is conveniently effected by passingcyanogen into a mixture of the-amine catalyst and a primary rnonohydricsaturated or unsaturated aliphatic or aromatic alcohol to be esterified.Alternatively, and particularly for the cyanogenization of higheralcohols which may be solids at ordinary temperatures, or when gaseousamines such as trimethyl amine are employed as catalysts, the reactionadvantageously also can take place in a solvent medium inert to thereaction, for example in ethers, esters, or hydrocarbon solvents. Thealcohols reacted, as mentioned just above, are those whose cyanformicacid esters can be formed by the conventional prior art esterificationreactions earlier described, and include ethylenically andacetylenically unsaturated materials such as allyl and propargylalcohols, as well as saturated monohydric alcohols, and aromaticmaterials having a primary alcohol group, such as benzyl alcohol. Thealcohols may be substituted with groups non-reactive with cyanogen. Theprimary monohydric aliphatic alcoholic materials also include partiallyesterified polyhydric materials such as glycolmonoacetate andglycolmonomethacrylate. Advantageously at least an equimolar amount ofalcohol is contacted with cyanogen in the reaction.

After reaction, the cyanformimide esters formed can conveniently beseparated in pure form from the reaction mixture by conventionaltechniques such as crystallization or distillation, suitably after priorneutralization of the basic catalyst.

A better understanding of the invention and of its many advantages canbe had by referring to the following specific examples given by way ofillustration.

Example 1 Example 2a Cyan-formimide allyl ester was prepared by passing28.2 gm. of cyanogen over a two hour period with stirring and at about 5C. into 30 gm. of allyl alcohol containing 1.5 .gm. of tri-butyl amine.On distillation, 51.8 gm. of cyanformimide allyl ester (86.9% of theory)were obtained. The product had a boiling point of 60 C. at 25 mm-./Hgand an 11 of 1.4450.

Example 2b Cyan-formimide allyl ester was prepared under the conditionsof Example 2a by passing 30.2 gm. of cyanogen into a mixture of 50 gm.of allyl alcohol and 2.5 gm. of tributyl amine. The reaction mixture wassubsequently neutralized with 1.55 of acetic acid and then distilled invacuum. The yield was 61.65 gm. of reaction product, or 96.5% of theory.

Example 3 Cyanrormimide propyl ester was prepared by reacting gm. ofn-propanol with 61.2 gm. of cyanogen under the conditions of Example 1and in the presence of 6 gm. of tributyl amine. After neutralizationwith acetic acid, the resulting mixture was distilled. The yield offinal product was 107.7 gms., or 81.7% of theory. The product had aboiling point of 545 C. at 20 mm./Hg and an n of 1.4239.

Example 4 Cyanformimide benzyl ester was prepared by reacting cyanogenand benzyl alcohol in the presence of 5% of triethyl amine using theprocedure of the earlier examples. After the usual recovery steps, ayield (81% of theory) of cyanformimide benzyl ester was obtained. Theproduct had a boiling point of 108 C. at 5 mm./Hg and an 11 of 1.5290.

Example 5 Cyanformimide 2-nitrob-utyl ester was prepared by passing 52of cyanogen over a two hour period into a Example 6 Cyanfonmimidefi-chloroethyl ester was prepared by passing 52 gm. of cyanogen into asolution of 80.5 gm. of B-chloroethyl alcohol and 4 gm. of diethylbutylamine in 100 ml. of ethylacetate over a period of three hours and at atemperature between 5 C. and 10 C. After neutralization of the tertiaryamine with propionic acid, the cyanformimide B-ch1oroethyl ester wasisolated from the reaction mixture by distillation. The yield was 118gm., or 89% of theory. The boiling point of the product was 55-65 C. Onanalysis, N found: 20.3%. N calc.: 21.1%.

Although specific embodiments have been shown and described herein, itis to be'understood that they are illustrativc, and are not to beconstrued as limiting on the scope and spirit of the invention.

What is claimed is:

1. In the method for preparing cyanformimide esters by reaction of aprimary monohydric alcohol with cyanogen in the presence of an alkalinecatalyst, the improvement of reacting said alcohol and cyanogen at atemperature between about 0 and about C. in the presence of a trialkylamine in which the alkyl groups each have from 1 to 6 carbon atoms,whereby the formation of oxalic acid di-imide esters is avoided.

2. A method as in claim 1 wherein said alcohol and cyanogen are reactedat a temperature between about 0 C. and about 20 C.

3. A method as in claim 1 wherein atleast an equimolar amount of alcoholis contacted with cyanogen for reaction.

References Cited by the Examiner UNITED STATES PATENTS 2,333,493 11/43Rigby.

OTHER REFERENCES Hahn et al.: Deutsche Chemische Gesellschaft Berichte,1935, vol. 68, pp. 19741986.

Woodburn et al.: Journal of Organic Chemistry, 1959, vol. 24, pp.210-214.

CHARLES B. PARKER, Primary Examiner.

1. IN THE METHOD FOR PREPARING CYANFORMIMIDE ESTERS BY REACTION OF APRIMARY MONOHYDRIC ALCOHOL WITH CYANOGEN IN THE PRESENCE OF AN ALKALINECATALYST, THE IMPROVEMENT OF REACTING SAID ALCOHOL AND CYANOGEN AT ATEMPERATURE BETWEEN ABOUT 0* AND ABOUT 50*C. IN THE PRESENCE OF ATRIALKYL AMINE IN WHICH THE ALKYL GROUPS EACH HAVE FROM 4 TO 6 CARBONATOMS, WHEREBY THE FORMATION OF OXALIC ACID DI-IMIDE ESTERS IS AVOIDED.